JP5401111B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus that detects the azimuth of a target from a phase difference of received signals.

  The millimeter wave radar device is mounted on a moving body such as a vehicle, and is widely used for surrounding monitoring in the forward and backward directions. A monopulse that detects (measures) the azimuth of the target based on the phase difference of the received signal at the receiving antenna unit that receives the reflected signal from the target as a method for detecting the azimuth of the target in the surrounding monitoring. There is a method. This monopulse system makes it possible to reduce the size of the radar apparatus and set its detection range to a relatively wide angle.

Here, in the monopulse radar device, when the interval between the receiving antennas for detecting the phase difference of the received signal is larger than the half wavelength of the transmitted signal, the phase difference exceeds the range of -180 deg to 180 deg. Since folding occurs, when a reflected signal is received from a target existing in the direction where phase folding occurs, there is a possibility that the direction of the target is erroneously detected in the monopulse method. Therefore, a technique for avoiding erroneous detection of a target direction due to phase folding is disclosed (for example, see Patent Document 1). In this technique, only when the azimuths of the targets detected by the two receiving antenna pairs having different antenna intervals coincide with each other, the coincident azimuth is adopted as the azimuth of the target detected by the radar device. Try to avoid false detection of targets.

JP 2000-230974 A

  In a monopulse radar apparatus, it is not easy from the viewpoint of manufacturing a practical radar apparatus to reduce the interval between the receiving antenna sections to be equal to or less than a half wavelength of the transmission signal so that phase wrapping does not occur. On the other hand, erroneously detecting the orientation of a target due to phase folding is not preferable for an application that uses the detection result of the radar device. For example, when a radar device is mounted in front of a vehicle and used to detect a target approaching the vehicle, depending on the state of phase wrapping that occurs, the situation in which an oncoming vehicle approaches from the front and the vehicle from the side It can be pointed out that there is a possibility of obtaining a detection result that is very similar to the direction of the opponent vehicle, which is the target, in the situation of the encounter where the person approaches. This is because phase wrapping occurs, and it is detected as if the target exists in the direction where the target does not actually exist. In this specification, the presence of this false target is detected. May be referred to as “ghost”.

  Then, since it is not preferable to transmit an erroneous detection result regarding the azimuth of the target to the driver of the vehicle, in such a case, the detection azimuth as the radar device is not output in the conventional technique. For this reason, detection of the direction of the target is left to the operator of the vehicle.

  The present invention has been made in view of such a problem, and in a monopulse radar device, by accurately excluding information on ghosts generated due to phase folding, the actual orientation of a target can be determined. An object of the present invention is to provide a radar device that can accurately detect.

  In order to solve the above-described problem, in the present invention, the reflected signal that reaches each receiving antenna unit from the target can be regarded as parallel, and the antenna between the receiving antenna units is a structural correlation of the receiving antenna unit. Focusing on the ratio of the intervals, the actual orientation of the target is detected by accurately calculating the number of phase folds in the signal received by the receiving antenna unit using the ratio. Since the ratio of the antenna interval between the receiving antenna parts is constant regardless of the incident angle of the reflected signal reaching from the target (that is, the direction of the target), it can be received regardless of the direction of the target. The number of phase wraps of the signal can be calculated accurately.

  Specifically, the present invention includes a transmission antenna unit that transmits a signal for detecting the orientation of a target, a reflected signal obtained by reflecting the transmission signal from the transmission antenna unit by a target, and A radar apparatus comprising: three or more receiving antenna units arranged on a line; and an azimuth detecting unit that detects an azimuth of the target from a phase difference of received signals reaching each of the three or more receiving antenna units. is there. In the radar apparatus, the three or more receiving antenna units include a first antenna pair including two receiving antenna units forming a first interval as an antenna interval, and an antenna interval different from the first interval. A second antenna pair including two receiving antenna units forming a second interval, wherein the azimuth detecting unit includes a ratio between the first interval and the second interval, the first antenna pair, and the first antenna unit. Based on the phase difference of the received signal in each of the two antenna pairs, calculate the number of phase wraps in at least one of the first antenna pair and the second antenna pair, and use the number of phase wraps. The direction of the target is detected.

  The radar apparatus according to the present invention includes at least two antenna pairs formed by two receiving antenna units. In each of the antenna pairs, it is possible to detect the azimuth of the target based on the phase difference of the received signal by the monopulse method. Here, as described above, in the monopulse system, erroneous detection of the target direction due to the phase folding of the received signal may occur. However, in the radar apparatus according to the present invention, the first interval and the second interval, which are different antenna intervals. By using the ratio to the interval (hereinafter also referred to as “antenna interval ratio”), the phase wrapping of the received signal is calculated, and erroneous detection of the target direction is avoided.

  The ratio of the antenna interval formed by the receiving antenna units arranged in a straight line is based on the fact that a reflected signal parallel to the target is incident on each receiving antenna unit for detecting the direction in the monopulse method. It can be understood from the structural correlation between the receiving antenna portions that the phase difference used is the same as the ratio between each antenna pair. And even if the incident angle of a reflected signal changes, the ratio between each antenna pair of the said phase difference does not change. Therefore, when detecting the azimuth of the target based on the phase difference in the monopulse method, the antenna spacing ratio can be used to accurately grasp the number of phase wraps without being affected by the azimuth of the target. It is possible to accurately detect the actual orientation of the.

  Here, in the radar device described above, one of the three reception antenna units overlaps to form the first antenna pair and the second antenna pair, and further, the remaining two except for the redundant reception antenna units. A third antenna pair having a third interval as an antenna interval different from the first interval and the second interval by one receiving antenna unit, and the azimuth detecting unit includes the first interval and the second interval Based on the ratio between the interval and the third interval, and the phase difference of the received signals in each of the first antenna pair, the second antenna pair, and the third antenna pair, the first antenna pair, the second antenna pair, The number of phase folds in each of the antenna pair and the third antenna pair may be calculated, and the direction of the target may be detected using the number of phase folds.

That is, by using the three receiving antenna units, it is possible to form three antenna pairs having different antenna intervals. Therefore, it is possible to detect the direction of the target efficiently and efficiently with a small number of receiving antennas. Note that the number of receiving antenna units may be four or more. In this case, it is possible to easily realize more accurate target orientation detection by appropriately selecting an antenna pair.

  Further, in the radar apparatus, the azimuth detecting unit relates to a provisional azimuth of the target tentatively from a phase difference of received signals in each of the first antenna pair, the second antenna pair, and the third antenna pair. A phase difference between the received signal and the direction of the target, which are determined by the number of phase wrapping, from the data related to the temporary direction of the target acquired by the provisional direction acquisition unit that acquires data and the temporary direction acquisition unit An azimuth determining unit that excludes azimuth ghost data that is not related to the actual azimuth of the target based on the correlation with the angle and determines the actual azimuth of the target may be included.

  In the above configuration, by using the correlation between the phase difference of the received signal and the azimuth angle of the target, which is determined using the number of phase wrapping of the received signal at each antenna pair calculated from the antenna interval ratio. Based on the number of phase folds, it is possible to specify a range of azimuths where it is determined that a target cannot exist. Therefore, by excluding the data related to the range of the azimuth where the target cannot exist as the azimuth ghost data from the data regarding the tentative azimuth of the target acquired by the temporary azimuth acquisition unit, the target is actually It is possible to output the existing orientation accurately.

  The provisional azimuth obtaining unit obtains data related to the provisional azimuth of the target by performing a fast Fourier transform process on the reception signals received by the three receiving antenna units, and the azimuth determining unit includes The azimuth ghost data may be excluded from data related to the provisional azimuth of the target obtained through fast Fourier transform by the provisional azimuth acquisition unit. With this configuration, the azimuth ghost data is excluded by the azimuth determining unit, and all signals received within a range in which the receiving antenna can receive the reflected signal from the target are subjected to a fast Fourier transform process. It will be done on data. Therefore, according to the radar apparatus according to the present invention, it is possible to accurately detect the azimuth of the target existing in the widest possible range.

  Here, in the radar apparatus up to the above, the azimuth determination unit excludes the exclusion data obtained by excluding the azimuth ghost data from the data related to the provisional azimuth of the target when the exclusion data has a predetermined continuity. Data may be determined as the actual orientation of the target. If the orientation of the target to be detected changes discontinuously, it is considered that there is some error in the calculated exclusion data itself. Therefore, by ensuring a predetermined continuity in the continuity of the exclusion data necessary for detecting the direction of the target, the direction of the target can be detected more reliably. Various methods can be adopted for detection of the predetermined continuity. For example, when the amount of change from the immediately preceding excluded data is within the predetermined range, it is determined that the predetermined continuity exists. May be. In this case, the exclusion data immediately before use may be plural.

  Moreover, the radar apparatus according to the present invention described above may be mounted on a moving body such as a vehicle, or may be mounted on an object that does not move.

  In a monopulse radar device, it is possible to accurately detect the actual orientation of a target by accurately excluding information on ghosts generated due to phase folding.

It is a figure showing the schematic structure of a radar apparatus in the Example of this invention. It is a figure which shows the locus | trajectory of the vehicle which is a target in the condition at the time of the situation at the time of the approaching vehicle and the situation at the time of the crossing of an oncoming vehicle detected by the conventional radar apparatus. It is a figure for demonstrating the path difference resulting from the structure of the receiving antenna in the radar apparatus shown in FIG. It is a figure which shows the correlation with the phase difference between the receiving antennas of the radar apparatus shown in FIG. 1, and the incident angle of the reflected wave from a target. It is a flowchart which shows the flow of the signal processing for target detection performed with the signal processing circuit of the radar apparatus shown in FIG.

  Here, an embodiment of a radar apparatus according to the present invention will be described with reference to the accompanying drawings. In addition, the said Example shows an example of the control apparatus which concerns on this invention, and does not limit the right range of this invention.

  The main specifications of the radar apparatus 1 shown in FIG. 1 are a frequency band of 76 GHz, a distance measurement method is an FM-CW (frequency modulation continuous wavelength) method, and an angle measurement method is a monopulse method. It is possible to detect the velocity and the direction (angle θ) with respect to the target. The radar apparatus 1 includes reception antennas 2 to 4, a transmission antenna 5, a signal processing circuit unit 10, and an oscillator 20 as main components. In FIG. 1, the receiving antennas 2 to 4 are illustrated, but these are illustrated as a part of a receiving antenna array including a receiving antenna (not shown). Here, the receiving antennas 2 to 4 are arranged on a straight line, and when the wavelength of the transmission wave emitted from the transmitting antenna 5 is λ, the interval between the receiving antenna 2 and the receiving antenna 3 is 6 / 4λ, 3 and the receiving antenna 4 are arranged so that the distance between the receiving antenna 4 and the receiving antenna 4 is 5 / 4λ, and thus the distance between the receiving antenna 2 and the receiving antenna 4 is 11 / 4λ, so that each receiving antenna forms the three antenna pairs shown here. Has been. In addition, a voltage control type oscillator 20 is connected to the transmission antenna 5. The oscillator 20 outputs, as a transmission signal, a signal obtained by subjecting a carrier wave having a predetermined frequency to triangular wave modulation having a predetermined frequency modulation width by a control voltage supplied from the signal processing circuit 14 included in the signal processing unit 10. Then, with this transmission signal, a transmission wave of wavelength λ is radiated from the transmission antenna 5, and the target is detected.

The mixers 11 to 13 are connected to the receiving antennas 2 to 4, respectively. Each mixer receives a local signal that is a part of the transmission signal from the oscillator 20, and the received signal received by each of the receiving antennas 2 to 4 and the local signal are mixed and mixed in each mixer. Downconverted to frequency. By this down-conversion, an FM-CW beat signal (a difference signal between a transmission signal and a reception signal) in the radar apparatus 1 is obtained. The signal processing circuit 14 together with the mixers 11 to 13 detects the distance, relative speed, and direction with respect to the target by performing an FFT (Fast Fourier Transform) process or the like on the beat signal obtained through each mixer. To do. Therefore, the signal processing circuit 14 forms an azimuth detecting unit of the radar apparatus according to the present invention. Note that the calculation method of the distance to the target and the relative velocity by the FM-CW method using the triangular wave modulation is a known technique, and the description thereof is omitted in this specification.

  Here, the orientation relative to the target (the orientation indicated by θ in FIG. 1) is calculated according to a so-called monopulse method. As is conventionally known, in a monopulse radar device, the direction of a target is determined based on a phase difference of a received signal caused by a path difference existing between two receiving antennas included in the antenna pair. θ is detected.

However, in the conventional monopulse radar device, if the received signal has a phase wraparound due to the path difference between the antenna pairs, the phase difference of the received signal directly detected between the receiving antennas is not necessarily the target. May not accurately reflect the incident angle θ of the reflected wave (that is, the orientation θ of the target). That is, the phase difference of the received signal at each antenna pair directly obtained by the signal processing circuit 14 through each mixer does not take into account the phase wrapping, and therefore, using this direct phase difference, the azimuth θ of the target is determined. When trying to detect, the presence (ghost) of a false target may be erroneously detected at a position where the target does not exist. FIG. 2 shows an example of the erroneous detection. FIG. 2A shows a detection result of the conventional monopulse method in a situation where a target vehicle is approaching the radar apparatus from the front (that is, a situation where an oncoming vehicle is present). In this case, a fake target (ghost) that does not exist is detected diagonally to the left together with the presence of the oncoming vehicle that should be detected. On the other hand, FIG. 2B shows a detection result of the conventional monopulse system in a situation where the target vehicle is about to cross from the left of the radar apparatus (that is, a meeting vehicle is present). It is. In this case, the presence of an encounter vehicle that should be detected is detected. Here, comparing FIGS. 2A and 2B, the ghost trajectory erroneously detected in the presence of the oncoming vehicle is very similar to the trajectory of the encounter vehicle detected in the presence of the encounter vehicle. I understand that Then, in the conventional monopulse radar device, it is impossible to accurately distinguish the oncoming vehicle and the encounter vehicle, and for vehicles equipped with the radar device, detection of the oncoming vehicle or the like is not limited for safety. First of all, the capability of the radar device was significantly reduced.

  Therefore, in the radar apparatus 1 according to the present invention, the monopulse method is adopted as a conventional angle measurement method. However, in the phase difference of the received signal due to the reflected wave from the target between the two receiving antennas in the monopulse method, the reception is performed. By taking into account the phase wrapping based on the structural correlation of the antennas (that is, the antenna interval), it is possible to accurately detect the azimuth θ of the target. Hereinafter, a detailed method for detecting the azimuth θ of the target in the radar apparatus 1 will be described.

  FIG. 3 is a diagram schematically showing an incident path when the reflected wave reflected by the target is incident on the receiving antennas 2 to 4. As can be seen from FIG. 3, there is a path difference L6 between the receiving antenna 2 and the receiving antenna 3, and similarly, between the receiving antenna 3 and the receiving antenna 4 and between the receiving antenna 2 and the receiving antenna 3. There are path differences of L5 and L11 between the antenna 4 and the antenna 4, respectively. Since the target is located sufficiently far from the radar apparatus 1, the incident angle of the reflected wave with respect to each receiving antenna may be considered as the same θ. Therefore, although the lengths of L5, L6, and L11 change according to the incident angle θ of the reflected wave, the ratio L5: L6: L11 of each path difference is constant regardless of the incident angle θ of the reflected wave. . This is because the reflected waves incident on each of the receiving antennas 2 to 4 are parallel, and thus include geometric differences including path differences L5, L6, and L11, and receiving antenna intervals 5 / 4λ, 6 / 4λ, and 11 / 4λ. This is because triangles similar to each other are formed.

In the radar apparatus 1, the interval between the receiving antennas 2 to 3 is 6 / 4λ, the interval between the receiving antennas 3 to 4 is 5 / 4λ, and the interval between the receiving antennas 2 to 4 is 11 / 4λ. From the geometric similarity shown, the ratio L5: L6: L11 of each path difference is 5: 6: 11 regardless of the incident angle θ of the reflected wave. Here, the phase differences of the received signals caused by the path differences L5, L6, and L11, and the phase differences taking into account the phase wrapping caused by the path differences are A5, A6, and A11 (each unit is deg), On the other hand, the phase difference that does not take into account the phase wrapping caused by each path difference, that is, the phase difference detected by the signal processing unit 14 directly through each mixer is a5, a6, a11 (each unit is deg). Then, A5, A6, A11
For a5, a6, and a11, the following correlation is established.
A5 = a5 + 360 · x (x: number of phase wraps at path difference L5)
A6 = a6 + 360 · y (y: number of phase wraps at path difference L6)
A11 = a11 + 360 · z (z: number of phase folds at the path difference L11)

And the phase differences A5, A6, A11 in which the phase wrapping is considered are, so to speak, the path differences L5,
Since L6 and L11 are phase-converted, the relationship A5: A6: A11 = L5: L6: L11 = 5: 6: 11 is established. On the other hand, a constant correlation is not established for the phase differences a5, a6, and a11 that are directly detected via the receiving antenna and the mixer and do not consider the phase folding. Therefore, the radar apparatus 1 uses a predetermined condition that is established based on the distance between the receiving antennas between A5, A6, and A11, and accurately grasps the phase wrapping caused by each path difference, thereby obtaining a monopulse. This method makes it possible to detect an accurate azimuth θ of the target.

上記式の左項は、各受信アンテナからの直接の検出値より算出される。また右項のうち-360xは、位相計算においては無視できる。また、右項のうち300yについては、位相を-180deg〜180degの範囲で表示することを考慮し、60y'と表示を変更したものであり、実質的な変更ではない。上記の式が意味するところは、各受信アンテナからの直接の検出値（左項）を利用して、整数となる位相折り返し数ｙ（ｙ’）を算出することが可能であるということである。そして、算出された位相折り返し数を用いて、ｙ（ｙ’）に対応する経路差Ｌ６の距離が算出でき、以て受信アンテナ２〜３の間隔との相関により三角関数を用いて、反射波の入射角θを下記式に従って算出できる。
θ＝Arcsin(L6/(6/4λ))=Arcsin(λ(a6+360y(y'))/360/(6/4λ)) First, attention is focused on the correlation between the path differences L5 and L6. Since L5: L6 = 5: 6 holds regardless of the incident angle θ of the reflected wave, A5: A6 = 5: 6 also holds. Therefore, the following equation holds.

The left term of the above equation is calculated from the detected value directly from each receiving antenna. In the right term, -360x can be ignored in the phase calculation. In addition, regarding 300y in the right term, the display is changed to 60y ′ in consideration of displaying the phase in the range of −180 deg to 180 deg, and is not a substantial change. The above expression means that it is possible to calculate the number of phase wrapping y (y ′) that is an integer by using the direct detection value (left term) from each receiving antenna. . Then, the distance of the path difference L6 corresponding to y (y ′) can be calculated using the calculated number of phase folds, and thus the reflected wave is calculated using a trigonometric function based on the correlation with the interval between the receiving antennas 2 to 3. Can be calculated according to the following equation.
θ = Arcsin (L6 / (6 / 4λ)) = Arcsin (λ (a6 + 360y (y ')) / 360 / (6 / 4λ))

上記式の左項は、各受信アンテナからの直接の検出値より算出される。また右項のうち-360yは、位相計算においては無視できる。また、右項のうち196zについては、位相を-180deg〜180degの範囲で表示することを考慮し、164z'と表示を変更したものであり、実質
的な変更ではない。上記の式が意味するところは、各受信アンテナからの直接の検出値（左項）を利用して、整数となる位相折り返し数ｚ（ｚ’）を算出することが可能であると
いうことである。そして、算出された位相折り返し数を用いて、ｚ（ｚ’）に対応する経路差Ｌ１１の距離が算出でき、以て受信アンテナ２〜４の間隔との相関により三角関数を用いて、反射波の入射角θを下記式に従って算出できる。
θ＝Arcsin(L11/(11/4λ))=Arcsin(λ(a11+360z(z'))/360/(11/4λ)) Similarly, attention is paid to the correlation between the path differences L6 and L11. Since L6: L11 = 6: 11 holds regardless of the incident angle θ of the reflected wave, A6: A11 = 6: 11 also holds. Therefore, the following equation holds.

The left term of the above equation is calculated from the detected value directly from each receiving antenna. In the right term, -360y can be ignored in the phase calculation. In addition, regarding 196z in the right term, the display is changed to 164z ′ in consideration of displaying the phase in a range of −180 deg to 180 deg, and is not a substantial change. What the above equation means is that it is possible to calculate the number of phase wrapping z (z ′) that is an integer by using a direct detection value (left term) from each receiving antenna. . Then, the distance of the path difference L11 corresponding to z (z ′) can be calculated using the calculated number of phase folds, and thus the reflected wave is calculated using a trigonometric function based on the correlation with the interval between the receiving antennas 2 to 4. Can be calculated according to the following equation.
θ = Arcsin (L11 / (11 / 4λ)) = Arcsin (λ (a11 + 360z (z ')) / 360 / (11 / 4λ))

上記式の左項は、各受信アンテナからの直接の検出値より算出される。また右項のうち-360zは、位相計算においては無視できる。また、右項のうち792xについては、位相を-180deg〜180degの範囲で表示することを考慮し、72x'と表示を変更したものであり、実質的な変更ではない。上記の式が意味するところは、各受信アンテナからの直接の検出値（左項）を利用して、整数となる位相折り返し数ｘ（ｘ’）を算出することが可能であるということである。そして、算出された位相折り返し数を用いて、ｘ（ｘ’）に対応する経路差Ｌ５の距離が算出でき、以て受信アンテナ３〜４の間隔との相関により三角関数を用いて、反射波の入射角θを下記式に従って算出できる。
θ＝Arcsin(L5/(5/4λ))=Arcsin(λ(a5+360x(x'))/360/(5/4λ)) Similarly, attention is paid to the correlation between the path differences L11 and L5. Since L11: L5 = 11: 5 holds regardless of the incident angle θ of the reflected wave, A11: A5 = 11: 5 also holds. Therefore, the following equation holds.

The left term of the above equation is calculated from the detected value directly from each receiving antenna. In the right term, -360z can be ignored in the phase calculation. In addition, 792x in the right term is a display that is changed to 72x ′ in consideration of displaying the phase in a range of −180 deg to 180 deg, and is not a substantial change. The above equation means that the number of phase wrapping x (x ′) that is an integer can be calculated using the detection value (left term) directly from each receiving antenna. . Then, the distance of the path difference L5 corresponding to x (x ′) can be calculated using the calculated number of phase folds, and thus the reflected wave is calculated using a trigonometric function based on the correlation with the interval between the receiving antennas 3 to 4. Can be calculated according to the following equation.
θ = Arcsin (L5 / (5 / 4λ)) = Arcsin (λ (a5 + 360x (x ')) / 360 / (5 / 4λ))

  Thus, according to any one of Equations 1 to 3, the incident angle θ of the reflected wave can be calculated based on the structural correlation of the receiving antenna. Of course, the incident angle θ obtained from a plurality of equations is used to determine whether or not the calculated incident angle θ is deviated, and the final reflection is obtained by averaging the plurality of incident angles θ. It may be adopted as the value of the angle θ.

In addition, instead of directly calculating the reflection angle as described above, each of the above-mentioned in order to filter the ghost with respect to the detection result (for example, the result shown in FIG. 2) of the target orientation by the conventional monopulse method. The number of phase wraps due to the path difference may be used. That is, the functional unit for detecting the azimuth according to the prior art corresponds to the provisional azimuth obtaining unit of the radar apparatus according to the present invention, and the functional unit for performing the filtering corresponds to the azimuth determining unit of the radar apparatus according to the present invention. For this purpose, the angle area (incident angle θ is in the range) where the target is opposed to the radar apparatus 1 is roughly specified by using the number of phase wrapping at each path difference calculated from Equations 1 to 3. To do. FIG. 4 shows the correlation between the phase difference at each path difference and the incident angle θ of the reflected wave. The phase difference shown in FIG. 4 is a phase difference that does not reflect phase wrapping, that is, a phase difference directly detected via the receiving antenna and the mixer. At this time, due to the installation intervals of the receiving antennas 2, 3, 4 being 5 / 4λ, 6 / 4λ, and 11 / 4λ, the phase difference with respect to the incident angle θ is phase-turned at a predetermined incident angle. Specifically, the phase difference a5 corresponding to the path difference L5 is expressed by a5 = 5 / 2π sin θ, and therefore phase wrapping occurs when the incident angle θ is ± 23.6 deg.
Since the phase difference a6 corresponding to 6 is expressed by a5 = 3πsin θ, phase wrapping occurs when the incident angle θ is ± 19.5 deg, and the phase difference a11 corresponding to the path difference L11 is a11 = 11/2.
Since it is expressed by π sin θ, phase folding occurs when the incident angle θ is ± 10.5 deg, ± 33.1 deg, ± 65.4 deg. In consideration of the practicality of the radar device 1, the incident angle is in the range of ± 90 deg. Therefore, it is possible to determine from which angle area the reflected wave from the target has arrived based on the number of turns x, y, z at each path difference obtained by the above formulas 1 to 3.

Based on the above, Table 1 below shows the correlation between the number of phase wraps at each path difference and the angle area where it is determined that the target exists.

For example, when no phase wrapping occurs in any path difference, the incident angle θ of the reflected wave is considered to belong to the angle area of R1 (−10.5 deg to 10.5 deg), and the path differences L6 and L11 When the phase fold occurs once each, the incident angle θ of the reflected wave is considered to belong to the angle area of R3 (19.5 deg to 23.6 deg). In addition, about the said angle area, each angle area of R2-R5 and each angle area of R2'-R5 'are set symmetrically on both sides of angle area R1.

Then, using the angle area determined based on the number of phase folds in the path difference shown in Table 1, the azimuth of the target obtained by measuring the angle of the conventional monopulse method is actually the target It is also possible to determine whether the direction is an existing direction or a direction due to a ghost. Then, data relating to the direction of the target determined to be a ghost based on the number of phase turns (corresponding to the direction ghost data in the present invention) is excluded from the data relating to the direction of the target obtained by the conventional monopulse method. By performing the filtering, it is possible to detect the actual orientation of the target. For example, if the example of the oncoming vehicle is used, since the oncoming vehicle is approaching, the radar apparatus 1 approaches from the front. Therefore, in this case, since the number of phase folds at each path difference is 0, it can be seen that the oncoming vehicle as the target is located in the angle area (-10.5 deg to 10.5 deg) of R1. Then, returning to FIG. 2, the trajectory that does not belong to this angle area is
It can be determined that the trajectory is caused by a ghost, and the presence of an oncoming vehicle can be accurately detected by the radar apparatus 1 by excluding (filtering) data relating to the ghost. That is, the functional unit that performs such filtering corresponds to the azimuth determining unit of the radar apparatus according to the present invention.

  Here, specific signal processing performed by the signal processing circuit 14 will be described with reference to FIG. FIG. 5 is a flowchart showing a flow of processing executed in the signal processing circuit 14. These processing contents are realized by various methods such as a predetermined analog circuit, a DSP (Digital Signal Processor), and an ECU (Electrical Control Unit).

In S101, an FFT (Fast Fourier Transform) operation is performed on each of a rising section (upbeat) and a falling section (downbeat) of the triangular wave of the beat signal generated in the FM-CW system, so that uppeak and Down peak extraction is performed. Next, in S102, the phase differences a5, a6, and a11 caused by the above-described path differences are calculated.
After that, as described above in S103, the phase differences A5, A6, A11 in which phase aliasing is considered and the number of phase aliases x and y in each path difference based on the structural correlation of the receiving antennas (interval between the receiving antennas). , Z are calculated.

  Here, the correlation between the number of phase folds and the angle area at each path difference shown in Table 1 is stored in advance in a storage device (memory or the like) in the signal processing circuit 14. In S104, in other words, the data regarding the ghost is excluded from the peak data extracted in S101 based on the number of phase folds calculated in S103 and the data regarding the angle area in the storage device. Only the peak data belonging to the angle area determined by the number of phase folds is left as data for target orientation detection. Thereby, the direction of the target is provisionally determined.

  Thereafter, in S105, a pairing process that is a one-to-one correspondence between the up peak and the down peak is performed, and the distance to the target is calculated from the sum of the frequencies of the two peaks, and the difference between the frequencies of the two peaks is calculated. The relative speed with the target is calculated. Next, continuity determination is performed in S106. In this processing, whether or not the azimuth, distance, and relative speed calculated in S104 and S105 are from the same target by collating with the azimuth, distance, and relative speed data of the immediately preceding target. Determine. For example, when the processing from S101 to S105 is repeated three times in succession, the data regarding the direction, distance, and relative speed obtained as a result is continuous, and it can be determined that these are data from the same target. Then, the data is determined as the target detected by the radar apparatus 1.

  By performing the processing shown in FIG. 5, it is possible to eliminate the influence of the data regarding the ghost caused by the phase wrapping, so that the target can be accurately detected. In particular, a method for removing ghost-related data (phase ghost data) using the data related to the correlation between the number of phase folds and the angle area shown in Table 1 is adopted for the data extracted by the FFT processing. Therefore, the process shown in FIG. 5 can be applied to any target, and the influence of ghost can be surely eliminated. In addition, even when a very similar trajectory can be obtained, such as the situation of the oncoming vehicle and the situation of the meeting vehicle shown in FIG. 2, the influence of the ghost can be eliminated. The vehicle (target) can be detected.

<Modification>
In the above-described embodiments, the radar apparatus having the FM-CW ranging means is disclosed. However, if the radar apparatus adopts the monopulse type angle measuring means, the structural correlation of the receiving antenna according to the present invention is obtained. The technology for eliminating the influence of the ghost used can be adopted regardless of the presence or absence of the FM-CW method. Further, the number of receiving antennas is not limited to three and may be four or more.

  The radar apparatus 1 is preferably installed on a moving body such as a vehicle. As an example, the radar apparatus 1 is installed on both the left and right sides of the front of the vehicle. Of course, the number of radar devices to be installed may be one or three or more.

DESCRIPTION OF SYMBOLS 1 ... Radar apparatus 2, 3, 4 ... Receive antenna 5 ... Transmit antenna 10 ... Signal processor 11, 12, 13 ... Mixer 14 ... Signal processing Circuit 20... Oscillator

Claims (3)

A transmission antenna unit for transmitting a signal for detecting the direction of the target;
Three or more receiving antenna units that receive a reflected signal in which a transmission signal from the transmitting antenna unit is reflected by a target and are arranged in a straight line;
An azimuth detecting unit that detects the azimuth of the target from the phase difference of the received signals reaching each of the three or more receiving antenna units,
The three or more receiving antenna units include a first antenna pair including two receiving antenna units that form a first interval as an antenna interval, and two that form a second interval as an antenna interval different from the first interval. A second antenna pair including a receiving antenna portion;
The first antenna pair and the second antenna pair are formed by overlapping one of the three reception antenna units, and the first interval is further determined by the remaining two reception antenna units excluding the overlapped reception antenna unit. And having a third antenna pair forming a third distance as an antenna distance different from the second distance,
The azimuth detecting unit includes a ratio between the first interval, the second interval, and the third interval, and a phase difference of received signals in each of the first antenna pair , the second antenna pair , and the third antenna pair. And calculating the number of phase folds in each of the first antenna pair , the second antenna pair , and the third antenna pair ,
From the phase difference of the received signal in each of the first antenna pair, the second antenna pair, the third antenna pair, obtain data related to the provisional azimuth of the provisional target,
Corresponding to the number of folds calculated for each antenna pair with reference to correlation data in which the number of folds in each of the first antenna pair, the second antenna pair, and the third antenna pair is associated with an angle area. A radar apparatus that obtains an angle area, excludes azimuth ghost data outside the angle area, and determines a provisional azimuth belonging to the angle area as an actual target azimuth . The azimuth detecting unit obtains data related to the provisional azimuth of the target by performing a fast Fourier transform process on the received signals received by the three receiving antenna units,
From data relating to the provisional orientation of the target object obtained through the high-speed Fourier transform, it excludes the azimuth ghost data,
The radar apparatus according to claim 1. The azimuth detecting unit, when the exclusion data obtained by excluding the azimuth ghost data from the data related to the provisional azimuth of the target has a predetermined continuity, the exclusion data is used as the actual azimuth of the target. decide,
The radar apparatus according to claim 1 or 2.

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